Selective dehydration of glycerol to acrolein: development of efficient and robust solid acid catalyst MUICaT-5

Abstract

Valorization of bioglycerol to industrially relevant products has been targeted worldwide to make biodiesel production cost competitive. Among several bulk chemicals derived from glycerol, synthesis of acrolein/acrylic acid is one route which is favored for which several catalysts and processes have been proposed in the literature. The present work reports on gas phase dehydration of glycerol to acrolein by using several catalysts and supports. Dodecatungstophosphoric acid supported (DTP) on hexagonal mesoporous silica (HMS) showed promise. It was observed that HMS acted as a better support for acrolein selectivity as compared to K-10 clay and octahedral molecular sieves (OMS). 20% w/w DTP/HMS catalyst resulted in 94% of glycerol conversion and 80% of acrolein selectivity at 225 °C. However, it suffered with severe deactivation due to coke deposition. Various techniques such as NH₃-TPD, BET-surface area, SEM image and EDX analysis were used for catalyst deactivation study. Then a new robust catalyst, MUICaT-5, was then synthesized by using deactivation data of 20% w/w DTP/HMS catalyst. MUICaT-5 catalyst gave 86% of glycerol conversion and 60% of acrolein selectivity. The stability and activity of the MUICaT-5 catalyst were evaluated by time on stream (TOS) studies up to 100 h at 275 °C. After regeneration, reusability of MUICaT-5 catalyst was carried out up to six times, without affecting acrolein selectivity and glycerol conversion. Catalyst reusability was also supported by characterization using NH₃-TPD, BET-surface area measurements, SEM, and EDX techniques.